2026-05-23T17:06:52Zhttps://keep.lib.asu.edu/oai/request

oai:keep.lib.asu.edu:node-1558882024-12-20T18:25:12Zoai_pmh:alloai_pmh:repo_items

155888 https://hdl.handle.net/2286/R.I.45940 http://rightsstatements.org/vocab/InC/1.0/ All Rights Reserved 2017 455 pages Doctoral Dissertation Academic theses Text eng Yousefi, Tara Diaz, Rodolfo E Cochran, Douglas Goodnick, Stephen Pan, George Arizona State University Doctoral Dissertation Electrical Engineering 2017 There is an ever-growing need for broadband conformal antennas to not only reduce the number of antennas utilized to cover a broad range of frequencies (VHF-UHF) but also to reduce visual and RF signatures associated with communication systems. In many applications antennas needs to be very close to low-impedance mediums or embedded inside low-impedance mediums. However, for conventional metal and dielectric antennas to operate efficiently in such environments either a very narrow bandwidth must be tolerated, or enough loss added to expand the bandwidth, or they must be placed one quarter of a wavelength above the conducting surface. The latter is not always possible since in the HF through low UHF bands, critical to Military and Security functions, this quarter-wavelength requirement would result in impractically large antennas.<br/><br/>Despite an error based on a false assumption in the 1950’s, which had severely underestimated the efficiency of magneto-dielectric antennas, recently demonstrated magnetic-antennas have been shown to exhibit extraordinary efficiency in conformal applications. Whereas conventional metal-and-dielectric antennas carrying radiating electric currents suffer a significant disadvantage when placed conformal to the conducting surface of a platform, because they induce opposing image currents in the surface, magnetic-antennas carrying magnetic radiating currents have no such limitation. Their magnetic currents produce co-linear image currents in electrically conducting surfaces.<br/><br/>However, the permeable antennas built to date have not yet attained the wide bandwidth expected because the magnetic-flux-channels carrying the wave have not been designed to guide the wave near the speed of light at all frequencies. Instead, they tend to lose the wave by a leaky fast-wave mechanism at low frequencies or they over-bind a slow-wave at high frequencies. In this dissertation, we have studied magnetic antennas in detail and presented the design approach and apparatus required to implement a flux-channel carrying the magnetic current wave near the speed of light over a very broad frequency range which also makes the design of a frequency independent antenna (spiral) possible. We will learn how to construct extremely thin conformal antennas, frequency-independent permeable antennas, and even micron-sized antennas that can be embedded inside the brain without damaging the tissue. Electrical Engineering Electromagnetism Antenna Conformal Antennas Electromagnetism magnetic antennas Magnetic materials Next Generation of Magneto-Dielectric Antennas and Optimum Flux Channels